Marijuana Impairment?

Marijuana impairment does exist. Recently we wrote a blog post highlighting an organization called NORML NORML is a marijuana advocacy group. We were surprised at the age of the studies (30 years) they quoted to support their advocacy of marijuana. We are presenting a more recent study, 2016, of the effects of marijuana on a person. We think it is important information for employers to know and use in support of their drug and alcohol free workplace policy.

The survey systematically review the empirical research published in the past decade (from January 2004 to February 2015) on acute and chronic effects of cannabis and cannabinoids and on persistence or recovery after abstinence. The study summarizes the findings into the major categories of the cognitive domains investigated, considering sample characteristics and associations with various cannabis use parameters. Verbal learning and memory and attention are most consistently impaired by acute and chronic exposure to cannabis. Psychomotor function is most affected during acute intoxication, with some evidence for persistence in chronic users and after cessation of use. Impaired verbal memory, attention, and some executive functions may persist after prolonged abstinence, but persistence or recovery across all cognitive domains remains under-researched. Associations between poorer performance and a range of cannabis use parameters, including a younger age of onset, are frequently reported. Little further evidence has emerged for the development of tolerance to the acutely impairing effects of cannabis. Evidence for potential protection from harmful effects by cannabidiol continues to increase but is not definitive. In light of increasing trends toward legalization of cannabis, the knowledge gained from this body of research needs to be incorporated into strategies to minimize harm. (Page 3)

Memory function has been the most consistently impaired cognitive domain affected by cannabis, and studies from the past 10 years continue to extend the evidence base. The most extensive evidence for impairment is within verbal learning and memory. (Page 5)

Verbal Learning and Memory. Most often measured using word list learning tasks, with several immediate and delayed recall trials and a recognition trial, verbal learning and memory tasks have been identified as particularly sensitive to the acute and chronic effects of cannabis. (Page 5)

Significant associations between poorer performance in regular users and frequency, quantity, duration, and age of onset of cannabis use have been reported. Consistent with previous finding, long-term users appear to be more affected than short-term users. (Page 7)

Similarly, chronic cannabis use was shown to impair working memory in young adults on immediate recall, verbal reasoning, and verbal n-back working memory tasks, (Page 7)

Numerous studies report impairment in adolescent and adult cannabis users with a wide range of exposure as well as former users abstinent for several weeks on measures of sustained and divided attention, processing speed, rapid visual information processing, visual search, tracking, trail making, and paced serial addition. Users abstinent for 23 days remained impaired relative to control subjects despite improvements in sustained and divided attention with increasing abstinence with poor attentional performance associated with younger age of onset in this study and another study of adolescents abstinent for 30 days. (Page 7)